408 THE DUCTLESS GLANDS 



mental histories of the two viscera are very different. As has 

 already been pointed out, the kidneys originally develop in 

 the pelvic region, and the retention of the pelvic position is a 

 well-recognised developmental anomaly. On the other hand, 

 the supra-renal glands develop in the abdomen, and they are 

 therefore found in their normal position on the posterior 

 abdominal wall, even when the kidney lies in the pelvis. 

 Histologically, the supra-renal gland consists of two parts, 

 which are well differentiated, namely, the cortex and the 

 medulla. These two parts differ from one another, not only 

 in appearance, but also in their functions and their mode of 

 development. Adrenalin is formed in the medulla of the 

 gland, while the cortex is functionally passive, and cortical 

 extracts have no marked actions, when introduced into the 

 body. The medulla of the supra-renal is developed by a 

 budding off of some of the cells of the lumbar sympathetic 

 system, whereas the cortex is simply a condensation of the 

 mesoderm, in which the medullary anlage is situated. This 

 connexion of the gland with the sympathetic system is of 

 interest in connexion with Addison's disease. 



In the majority of cases, post-mortem examination in 

 Addison's disease has revealed some lesion, usually tuber- 

 culous in origin, of the supra-renal glands. In a small 

 percentage of cases, the supra-renals have been normal in 

 appearance and structure, but examination of the coeliac 

 ganglia (p. 188), which lie close to the medial borders of the 

 supra-renals, has revealed the fact that they were the site of 

 tuberculous disease. In consequence, there are two different 

 theories with regard to the cause of Addison's disease. 

 The first, and most widely accepted, theory holds that the 

 condition is due to some pathological change in the supra- 

 renal glands, and that this change leads to alteration in the 

 nature of the internal secretion. This theory infers that the 

 administration of supra-renal extract is the rational line of 

 treatment to adopt. The use of this extract, though some- 

 times temporarily beneficial, cannot, however, be regarded as 



